1. Field of the Invention
The present invention relates to a droplet ejection device which ejects droplets onto a curved surface, and to a manufacturing method of the device.
2. Description of Related Art
As an example of a droplet ejection device which ejects droplets onto a curved surface, there has been known an ink-jet head disposed so as to face a cylindrical drum which holds a printing medium on its surface. A printing medium, which is held on the surface of the drum in a curved state, is conveyed as the drum rotates. Ink droplets are ejected from nozzles of the head to a printing surface of the printing medium, that is, an opposite surface of a surface of the printing medium facing the surface of the drum, and thereby printing is conducted. In this type of head, while the printing surface of a printing medium is curved corresponding to the curved surface of the drum, a droplet ejection surface of the head, on which a plurality of nozzles open, is flat. Because of this, the distance between the droplet ejection surface and the printing surface of the printing medium is not constant. This causes a problem of a deviation of ink landing position, that is, ink is not landed at a position where it should be landed, on the printing surface of the printing medium during printing.
In order to solve the above problem, it is preferable that the droplet ejection surface is parallel to the printing surface of a printing medium. For example, a head may be configured to be curved as a whole, the head including: a nozzle plate in which a plurality of nozzles are formed; a substrate in which pressure chambers respectively corresponding to the nozzles are formed; a diaphragm bonded to the substrate; and piezoelectric elements provided on the diaphragm so that the piezoelectric elements respectively correspond to the pressure chambers. As a result, the droplet ejection surface of the nozzle plate is configured to be curved.